Prognostic, predictive, and pharmacogenomic assessments of CDX2 refine stratification of colorectal cancer

We aimed to refine the value of CDX2 as an independent prognostic and predictive biomarker in colorectal cancer (CRC) according to disease stage and chemotherapy sensitivity in preclinical models. CDX2 expression was evaluated in 1045 stage I–IV primary CRCs by gene expression (n = 403) or immunohistochemistry (n = 642) and in relation to 5-year relapse-free survival (RFS), overall survival (OS), and chemotherapy. Pharmacogenomic associations between CDX2 expression and 69 chemotherapeutics were assessed by drug screening of 35 CRC cell lines. CDX2 expression was lost in 11.6% of cases and showed independent poor prognostic value in multivariable models. For individual stages, CDX2 was prognostic only in stage IV, independent of chemotherapy. Among stage I–III patients not treated in an adjuvant setting, CDX2 loss was associated with a particularly poor survival in the BRAF-mutated subgroup, but prognostic value was independent of microsatellite instability status and the consensus molecular subtypes. In stage III, the 5-year RFS rate was higher among patients with loss of CDX2 who received adjuvant chemotherapy than among patients who did not. The CDX2-negative cell lines were significantly more sensitive to chemotherapeutics than CDX2-positive cells, and the multidrug resistance genes MDR1 and CFTR were significantly downregulated both in CDX2-negative cells and in patient tumors. Loss of CDX2 in CRC is an adverse prognostic biomarker only in stage IV disease and appears to be associated with benefit from adjuvant chemotherapy in stage III. Early-stage patients not qualifying for chemotherapy might be reconsidered for such treatment if their tumor has loss of CDX2 and mutated BRAF. This work was financially supported by the Cancer Clinic, Oslo University Hospital (Grant No.: 2017-19 supporting JB with researcher fellowship), the Norwegian Cancer Society (Grant No.: 182759-2016, to RAL; and Grant No.: 6824048-2016, to AS), the foundation K. G. Jebsen Colorectal Cancer Research Centre, Stiftelsen Kristian Gerhard Jebsen, the South-Eastern Health Regional Authorities of Norway, and the Research Council of Norway, in cooperation with the University of Oslo, through the ?Toppforsk? grant (RAL, Project Number 250993/F20). This work was financially supported by the projects NORTE-01-0145-FEDER-000029 and NORTE-01-0145-FEDER-000003, supported by Norte Portugal Regional Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work was also supported by FEDER?Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020?Operational Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portuguese funds through FCT?Funda??o para a Ci?ncia e a Tecnologia/Minist?rio da Ci?ncia, Tecnologia e Inova??o in the framework of the project ?Institute for Research and Innovation in Health Sciences? (POCI-01-0145-FEDER-007274). RB acknowledges FCT for financial support (SFRH/BPD/68276/2010).